A 0.8 THz $f_{\rm MAX}$ SiGe HBT Operating at 4.3 K

We demonstrate record ac performance (0.8 THz) for a silicon-germanium heterojunction bipolar transistor (SiGe HBT) operating at cryogenic temperatures. An extracted peak f_MAX of 798 GHz (peak f_T of 479 GHz) at 4.3 K was measured for a device with a BV_CEO of 1.67 V. This scaled SiGe HBT also exhibits excellent thermal properties, as required from an electro-thermal reliability perspective. Taken together, these results strongly suggest that at the limits of scaling, robust, and manufacturable SiGe HBTs designed for room temperature operation are likely to achieve THz speeds.